Based on CFD method, the numerical simulation on side wall boundary layer of GAW-1 Multi-element airfoil with relative thickness for 17% was investigated, and compared with the results of Northwestern Polytechnical University's NF-3 low speed wind tunnel experiments. The results show that, in view of NF-3 wing model in wind tunnel pressure experiments, when the attack angle is less than 4°, the effect of wind tunnel side wall boundary layer on the span direction of airfoil can be neglected, when the attack angle is more than 4°, the effect of wind tunnel side wall boundary layer on the intermediate section of the flow field must be controlled and modified. It is verified that the NF-3 wind tunnel side wall boundary layer blowing system can effectively control side wall boundary layer interference and improve aerodynamic characteristic of airfoil.